Hydraulic brake system



Nov. 8, 1938. P. F. ROSSMANN `mllmAuLIC BRAKE SYSTEM` Filed Nov. 14, 1934 worwui www Patented Nov. 8, 19738 UNITED STATI-:s

PATENTV GFFICE HYDRAULIC ME SYSTEM Application November 14, 1934, Serial No. 758,053

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This invention 4relates to brake mechanism for motor vehicles and more particularly to improvements in apparatus for supplying fluid under pressure for the actuation of vehicle brakes. It

is the principal object of the invention to provide for the power application of the brakes, the usual manually operated brake ntrol means being employed merely to initiate and regulate the application of power to set the brakes.

1b. It is a feature of the invention that the manual ei'iort required in the application of the brakes is reduced to a minimum, thus making possible the same control of a vehicle by an operator having only slight physical strength and rendering the driving of the vehicle less tiresome. It is a further feature of the invention that the degree of braking action is substantially independent of the force exerted by the operator in applying the brakes, the effectiveness of the brakes being determined primarily by the extent to which the usualbrake pedal is depressed rather than by the magnitude of the pressure applied thereto.

It is a more spe'cic object of the invention to provide operating mechanism for a fluid acpressure device and means for multiplying the pressure delivered by the power device, in combination with a manually operable control mechanism therefor. In the preferred embodiment of the linvention the power driven device is actuated from the propulsion means of the vehicle, for instance from the motor, the drive shaft, or other moving part.

Further objects and features of the invention will be apparent from the following description, taken in connection with the accompanying drawing, in which:

Figure 1 is a side elevation of portions of a motor vehicle illustrating one method of applyv.irig the present invention thereto;

Figures'2 and 3 are sectional views, partly diagrammatic, illustrating the position occupied by the principal elements of apparatus embodying the invention in the released and fully applied positions respectively of the brakes;

Figure 4 is a sectional view taken substantially on the line 4-4 of Figure 2;

vFigure 5 is an enlarged sectional view of certain structure shown in Figure 1;

of certain structures shown in Figure 1.

In order to facilitate an understanding of the invention, specific language is employed'in describing the embodiment of the invention shown w'iin the ldrawing and selected for the purpose of .tuated brake employing a power driven fluidV Figure 6 is a further enlarged sectional view (Cl. BH2) illustrating the principles thereof. It will nevertheless be understood that no limitation of the scope of the invention is intended by the-use of such specific language,'various structural alteration's and modifications being contemplated such 5 as would occur to one skilled in the art to which the invention relates.

ReferringilrsttoFigureLitwillbeobserv that the vehicle. to which the invention is applied is provided with the usual motor Il, having asso- 10 ciated therewith a crank case Il. clutch housing, I2, andtransmission housing Il, the detailed construction of these umts forming no Vpart of the present invention. The vehicle is further provided with the usual vehicle wheels of which one is shown at i5, this wheel being provided with a brake drum il having expanding brake shoes i1 which are retained in the released position Vby a coil spring i8 acting therebetween and which may be s'et`by theapplication of iiuid 20 pressure to opposed pistons 2l disposed within a cylinder 2|, the latter being supplied with fluid under pressure from a piper22 communicating with the cylinder. The fluid employed may be the usual uid supplied with brake mechanism of this character. Thus when the necessary pressure is applied within the cylinder 2l, the pistons will move outwardly and will force the brake shoes i1 against the brake drum Il to frictionally retard the movement of the vehicle. The so iiuid brake system may comprise braking units of this character in association with all four wheels of the vehicle or with only two, it being appreciated that the present invention involves improvements in the apparatus by means ofk which pressure is applied to the working fluid; the structural details of the braking units associated with each wheel may assume any desired form.

The pipe 22 and a pipe 23 which may conduct o iluid to braking units associated with the front vehicle wheels, are supplied with fluid from a pipe 25 communicating with the interior of a housing indicated generally in Figure 1 at 21, this housing being preferably secured to the transmission housing I3 of the vehicle in any suitable manner. As shown more particularly in Figures 2 and 3, this housing preferably comprises a cylinder 2l having a piston 30 supported for reciprocation therein. ForwardLv of the cylinder 28, the housing 21 is provided with a portion 3| of reduced diameter, the internal wall of which serves a guide for the sleeve l2 which is carried by and preferably formed integrally with the piston 30. The sleeve 32 is provided interu mediate the ends thereof with an internal annular recess 88 and is relieved as indicated at 84 in Figure 4 to provide a plurality of circumferentially spaced, longitudinally extending passages intermediate the annular recess 88 and the end oi' the sleeve 82. The member 88 extends within the portion 8| oi' the housing 21 through packing 88 and is slidably received within the sleeve 82, this member having articulated connection at 4| with the lower end 48 of a brake pedal 42 which'is pivoted at 45 to the transmission housing and is normally rotated in a clockwise direction to the position in which it is shown in Figure 1 of the drawing by means of a spring 48 acting between the lower end of the pedal and the transmission housing.

The piston 88 is also provided with a rearwardly directed cylinder 48, secured thereto or formed integrally therewith, the cylinder 48 being provided with an annular recess 48 and being relieved as at 5I to provide a plurality of circumferentially spaced, longitudinally extending passages similar to the passages 84 in the sleeve 82. The interior oi' the cylinder 48 is dimensioned to receive a piston 58 which may be rigidly secured by means of a nut 58 to a cover member 54 which is bolted as at 55 to the rear end of the housing 21. Pipe 25 is secured within one end of the piston 58 and communicates with a passage 58 leading therethrough.

A conduit 88 which supplies uid under pressure to the cylinder 28 behind the piston 38 to actuate the latter is in communication with the interior of the cylinder and with a pump housing 82, the latter being in turn supplied with uid through a conduit 88 from a reservoir 84 which is shown in Figure 1 and diagrammatically in Figures 2 and 3. When the brakes are released and the parts occupy the position shown in Figure 2, fluid delivered to the cylinder 28 through the conduit 88 flows into a centrally disposed passage 85 in the piston 38 through a plurality of radially extending passages 88 and from thence in opposite directions past one-way valves into the cylinder 48 and the sleeve 32. These oneway valves may each consist of a ball 89 floating in a chamber 18 and retained therein by means of a lip 1| at the outer end oi' the chamber', the ball in the closed position of the valve seating against the end of the passage 85. One or more longitudinally extending grooves 14 are provided in each chamber 18 to ensure free movement of fluid from the passage 85 past the valves. Still referring to Figure 2, the iiuid passing into the cylinder 48 is discharged through the annular recess 48 and the passages 5| into the non-working portion of the cylinder 28. Discharge conduits 18 provide for the return of this uid to the reservoir 84.

Fluid emerging from the passage 65 into the sleeve 82 flows through the annular recess 33 and the passage 34, being returned to the reservoir through the conduit 18. A conduit 15 communicates with the non-working portion of the cylinder 28 and with the upper side of a storage reservoir 15". A further conduit 15' affords communication between the lower side of the reservoir 15" and the reservoir 84. The reservoir 15" may be constituted by the usual supply tank secured to the vehicle dash, this tank being occasionally charged with operating uld in order that the entire system may remain filled at all times, as is common in braking systems of this type.

Within the housing 82 a pump is provided, this pump being preferably oi the positive delivery type. Thus in the form of the invention illustrated herein, the pump comprises intermeshing, rotating toothed elements 88 which are suitably shrouded so that uid entering between the teeth oi' these elements is carried about the periphery of the housing 82 and is ejected at the opposite end of the housing through the conduit 88, this type of pump being wholly conventional and well understood. One oi' the toothed elements 88 is secured to a driving shaft 8| which, as shown in Figure 1, may extend .upwardly and carry at its upper end a gear 82 meshing with a worm 84 carried by or formed on the drive shaft 85 of the vehicle, the latter being connected in conventional manner through differential gearing to drive the rear vehicle road wheels. The gear 82 and shaft 8| may be supported in a housing for the vehicle drive* shaft or in a separate housing 88 secured to the rear wall oi' the transmission housing.

While the parts occupy the position in which they are shown in Figure 2 with` the vehicle brakes released, and while the pump elements 88 are being driven as hereinbefore indicated, fluid will be continuously circulated through the conduit 88 into the working end of the cylinder 28 and returned to the reservoir 84 through the conduits 18 and 18 as hereinbefcre described. If, however, it is desired to apply the brakes, and the pedal 42 is depressed, the member 88 will be moved longitudinally and to the right as shown in Figure 2, ilrst preventing the discharge o! uid through the annular recess 88 of the sleeve 32, and thereafter applying pressure to the uid within the sleeve 82 and to the right of the member 38 to close the valve leading from the passage 85. 0n continued depression of the pedal the piston 88 and associated parts will be carried to the right with the member 88, the cylinder 48 moving against the piston 58 to close the annular recess 49 and apply pressure to the fluid within the cylinder 48 to close the one-way valve leading therein from the passage 85. It will now be observed that discharge of fluid from the working end oi.' the cylinder 28 is prevented as the result of the sealing of the ends of the passage 85 by the balls 88, and the uid supplied under pressure by the pump elements 88 will be applied directly to the piston 38 to move the latter to the right. Since the area of the piston 88 is quite large as compared with the area of the piston 58, the iiuid pressure within the cylinder 48 will promptly be greatly multiplied and duid under very much higher pressure than that delivered by the pump elements 88 will be supplied through the pipe 28 to the brake units at the vehicle wheels.

In practice, this difference in the area of the pistons 38 and 58 should be suilicient to ensure the development of a fluid pressure at the road wheel brake units which will provide the maximum braking eiort required, while utilizing a power driven pump developing very low pressure, whereby the brake pedal may be operated with a minimum of effort.

Movement of the piston 38 to the right will continue so long as the member 38 extends sufiiciently far within the sleeve 82 to interrupt communication with the annular recess 88. In other Words, the arrangement just described constitutes a follow-up mechanism, it being necessary to continue the depression of the pedal 42 in order to maintain the movement of the piston 88 to the right. If the. depression of the pedal 42 ceases at any intermediate point, the piston 88 and the the pressure on the piston 30 and retarding further movement of the latter to the right. In

of its movement, the parts will occupy substantially the position in which they are shown in Figure 3 of the drawing, the brake units at the road wheels being then fully applied.

When it is desired to release the brake, the brake pedal 42 is permitted to rise and the return of the pistons 28 ofthe individual brake units will return the working fluid through the pipe 25 into the cylinder 48 and restore the piston 38 to the position in which itis shown in Figure 2. In order to ensure the return of the piston 30, and to compensate for any possible leakage in the system between the cylinder 48 and the individual brake units at the road wheels, a

Icoil spring 88 or other yielding means may be provided, this spring being preferably located within' the non-working end of the cylinder 28 and acting between the cover member 54 and the piston 30. A stop member 88, which is represented as formed in the cylinder 28 and adapted appreciated that such multiplication of pre:sure 1 is principally desirable when the car is moving forward at high speed, at which time the maximum braking effort is necessary.

It is oi course desirable that the brake applying mechanism be operated in equally effective manner whether the vehicle is moving forwardly or rearwardly. For this purpose any well-known type of automatically reversing gearing may be substituted for the simple worm drive 82, 84 so that unidirectional rotation of the pump elements llis attained regardless of the direction oi' rotation of the drive shaft 85. However, I prefer to employ the arrangement illustrated in Figures 2 and 3 ofthe drawing in which unidirectional ilow of iluid through the conduit 88' is secured regardless of the direction of rotation of which. the pump elements 8Il partake.

Thus the conduit 88 may be provided with a check valve 58, permitting fluid flow inthe conduit away from but not toward the pump. A return -conduit 51 communicates with the conduit 68 outwardly of the check valve 56 and is 'in turn provided with a check valve 58 permitting iluid ilow in the conduit 51 from the conduit 63 to the conduit 60, but preventing flow in the opposite direction. A check valve 6I in the conduit 63 is provided to prevent iluid ilow from the conduit 63 into the reservoir 64, while permitting flow in the opposite direction.

A conduit 61 provided with a check valve 68 allords communication between the conduit and the reservoir 64, the check valve 68 permitting fluid ilow from the reservoir 84 into the conduit 80 but preventing i'low in the opposite direction. v

It will be observed that with this arrangement when the gear elements are rotated in the direction indicated by the arrows in Figures 2 'and 3, fluid will be withdrawn from the reservoir 84 through the conduit 83 and discharged through vthe conduit 60 into the cylinder 28 as hereinbefore described. II, however, the vehicle is operated in the reverse direction, the pump elements 80 will rotate in a direction opposite to that shown by the arrows in Figures 2 and 3-with the result that fluid will be withdrawn from the reservoir 64 through the conduit 61 and through the lower portion of the conduit 60 into the pump, being discharged through the upper portion of thev conduit 63 and through the conduit 51 into the upper portion of the conduit 80 and thence to the cylinder 28. 'Ihis construction is intended to be illustrative only, it being possible to substitute other unidirectional ow pump systems for that shown herein.

It will be appreciated that cylinder 28 and piston 30, cylinder 48 and piston 58con`stitute a fluid motor-pump unit, and that the cylinders and pistons of the unit may be reversed in position and function without affecting the result. For instance, it is not material whether the piston 50 or the cylinder 48 is movable; relative movement is all that is required.

The manually operated member 38 constitutes in effect a control means for a il'uid by-pass, this by-pass moving with the piston 30 and the associated parts, and comprising recess 33 and passages 34. If desired, an additional by-pass connecting the delivery conduit 60 with either of the return conduits 16 or 18 may be provided, this by-pass being controlled'by a pressure operated check valve releasable. when a predetermined pressure is exceeded to ensure against the development of excessive pressures in the system.

It will be observed that the arrangementprovides a simple and effective device whereby iluid under high pressure may be supplied for the brakthe brake pedal being effected without increase in fluid pump, of a lluid motor comprising a cylinder and a piston reciprocable therein and operable by iiuid delivered by said power pump, a second iluid pump comprising a cylinder and a piston reciprocable therein and operable as a unit with said motor, an initially open discharge passage for iluid from said motor cylinder adapted to be closed on relative movement of said motor cylinder and piston, a second initially open discharge passage for fluid from said motor cylinder, manually operable means for closing said second discharge passage and initiating relative movement of said motor cylinder and piston to close said irst discharge passage, and means, including trapped iluid, transmitting thrust between said manually operable means and said second pump whereby the latter may be manually displaced independently of said first pump..

vehicles, the combination with a vehicle brake, of

mechanism responsive to iluid pressure for applying said brake, and means for supplying fluid under pressure to said mechanism, said means including a power driven fluid pump, a second pump operable by fluid delivered from said first pump and supplying uid to said mechanism under pressure substantially greater than that developed by said first pump, manually operable means for controlling the operation of said second pump, and means, including trapped uid transmitting. thrust between said manually operable means and said second pump whereby the latter may be manually displaced independently of said first pump to deliver fluid to said mechanism.

3. In a fluid operated brake system for motor vehicles, the combination with a vehicle brake, of mechanism responsive to fluid pressure fox` applying said brake. and means for supplying uid under pressure to said mechanism, said means including a powerl driven iluid pump, a second pump operable by fluid delivered from said first pump and supplying fluid to said mechanism under pressure substantially greater than that developed by said first pump, manually operable means for controlling the operation of said second pump, said manually operable means including a follow-up mechanism for initiating and determining the extent of operation of said second pump, and means, including trapped fluid, transmitting thrust between said manually operable means and said second pump whereby the latter may be manually displaced independently of said first pump to deliver iluid to said mechanism.

4. In a fluid operated brake system for motor vehicles, the combination with a vehicle brake, of mechanism responsive to iluid pressure for applying said brake, and means `for supplying iluid under pressure to said mechanism, said means including a power driven fluid pump, a fluid motor-pump unit driven by iiuid i'rom said power driven pump and delivering fluid to said mechanism, manually operable means for controlling the supply of motive fluid to said motor-pump unit, and means, including trapped iiuid, affording an operative thrust transmitting connection between said manually operable means and said unit for effecting operation of the latter independently of said power driven pump to deliver fluid to said mechanism.

5. In a uid operated brake system for motor vehicles, the combination mechanism responsive to uid pressure for applying said brake, and means for supplying iiuid under pressure to said mechanism, said means including a power driven fluid pump. a fluid motor-pumpunit driven by iluid from said power driven pump and delivering fluid to said mechanism, a by-pass for diverting motive Iiuid from said motor-pump unit, manually operable means for opening and closing said by-pass. and means, including trapped fluid, affording an operative thrust transmitting connection between said manually operable means and said unit for effecting operation ofthe latter independently of said power driven pump to deliver iluid to said mechanism.

6. In a fluid operated brake system for motor vehicles, the combination with a power driven fluid pump, a motor-pump unit operable by .iowpressure motive fluid from said power pump and delivering high-pressure uid to the brake, manually operable means for controlling the delivery of motive fluid to said motor-pump unit, and means, including trapped fluid, transmitting thrust between said manually operable means said unit whereby the latter may be manuallg7 :iisplaced to deliver iiuid to said mechanism.

PETER F. RGSSMAHN.

with a Vehicle braise, of 

